1 /* 2 * - - - - - - - - - 3 * g a l _ p r 0 0 4 * - - - - - - - - - 5 * 6 * This routine is part of the General Astrodynamics Library 7 * 8 * Description: 9 * 10 * Precession-rate part of the IAU 2000 precession-nutation models 11 * (part of MHB2000). 12 * 13 * This routine is an independent translation of a FORTRAN routine 14 * that is part of IAU's SOFA software collection. 15 * 16 * Status: 17 * 18 * canonical model. 19 * 20 * Given: 21 * 22 * date1,date2 d TT as a 2-part Julian Date (Note 1) 23 * 24 * Returned: 25 * 26 * *dpsipr,*deps d precession corrections (Notes 2,3) 27 * 28 * Notes 29 * 30 * 1) The TT date date1+date2 is a Julian Date, apportioned in any 31 * convenient way between the two arguments. For example, 32 * JD(TT)=2450123.7 could be expressed in any of these ways, 33 * among others: 34 * 35 * date1 date2 36 * 37 * 2450123.7 0.0 (JD method) 38 * 2451545.0 -1421.3 (J2000 method) 39 * 2400000.5 50123.2 (MJD method) 40 * 2450123.5 0.2 (date & time method) 41 * 42 * The JD method is the most natural and convenient to use in 43 * cases where the loss of several decimal digits of resolution 44 * is acceptable. The J2000 method is best matched to the way 45 * the argument is handled internally and will deliver the 46 * optimum resolution. The MJD method and the date & time methods 47 * are both good compromises between resolution and convenience. 48 * 49 * 2) The precession adjustments are expressed as "nutation components", 50 * corrections in longitude and obliquity with respect to the J2000 51 * equinox and ecliptic. 52 * 53 * 3) Although the precession adjustments are stated to be with respect 54 * to Lieske et al. (1977), the MHB2000 model does not specify which 55 * set of Euler angles are to be used and how the adjustments are to 56 * be applied. The most literal and straightforward procedure is to 57 * adopt the 4-rotation epsilon_0, psi_A, omega_A, xi_A option, and 58 * to add dpsipr to psi_A and depspr to both omega_A and eps_A 59 * (Wallace 2002). 60 * 61 * 4) This is an implementation of one aspect of the IAU 2000A nutation 62 * model, formally adopted by the IAU General Assembly in 2000, 63 * namely MHB2000 (Mathews et al. 2002). 64 * 65 * References 66 * 67 * Lieske, J.H., Lederle, T., Fricke, W. & Morando, B., "Expressions 68 * for the precession quantities based upon the IAU (1976) System of 69 * Astronomical Constants", Astron.Astrophys., 58, 1-16 (1977) 70 * 71 * Mathews, P.M., Herring, T.A., Buffet, B.A., "Modeling of nutation 72 * and precession New nutation series for nonrigid Earth and 73 * insights into the Earth's interior", J.Geophys.Res., 107, B4, 74 * 2002. The MHB2000 code itself was obtained on 9th September 2002 75 * from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A. 76 * 77 * Wallace, P.T., "Software for Implementing the IAU 2000 78 * Resolutions", in IERS Workshop 5.1 (2002) 79 * 80 * This revision: 81 * 82 * 2005 August 24 ( c version 2008 January 19 ) 83 * 84 * 85 * Copyright (C) 2008 Paul C. L. Willmott. See notes at end. 86 * 87 *----------------------------------------------------------------------- 88 */ 89 90 #ifndef _GAL_PR00_H_ 91 #define _GAL_PR00_H_ 1 92 93 #undef __BEGIN_DECLS 94 #undef __END_DECLS 95 #ifdef __cplusplus 96 #define __BEGIN_DECLS extern "C" { 97 #define __END_DECLS } 98 #else 99 #define __BEGIN_DECLS /* empty */ 100 #define __END_DECLS /* empty */ 101 #endif 102 103 __BEGIN_DECLS 104 105 void 106 gal_pr00 107 ( 108 double date1, 109 double date2, 110 double *dpsipr, 111 double *depspr 112 ) ; 113 114 __END_DECLS 115 116 #endif /* !_GAL_PR00_H_ */ 117 118 /* 119 * gal - General Astrodynamics Library 120 * Copyright (C) 2008 Paul C. L. Willmott 121 * 122 * This program is free software; you can redistribute it and/or modify 123 * it under the terms of the GNU General Public License as published by 124 * the Free Software Foundation; either version 2 of the License, or 125 * (at your option) any later version. 126 * 127 * This program is distributed in the hope that it will be useful, 128 * but WITHOUT ANY WARRANTY; without even the implied warranty of 129 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 130 * GNU General Public License for more details. 131 * 132 * You should have received a copy of the GNU General Public License along 133 * with this program; if not, write to the Free Software Foundation, Inc., 134 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 135 * 136 * Contact: 137 * 138 * Paul Willmott 139 * vp9mu@amsat.org 140 */ 141